Diagnostic ultrasound has provided an incredible wealth of knowledge in medicine. Few would be willing to deny the impact this modality has had on patient care, particularly women and children. With millions of ultrasound examinations performed each year, ultrasound remains one of the fastest growing imaging modalities. This growth is due to its low cost, real-time image display, and, to no lesser extent, its apparent lack of bioeffects. The regulatory process that controls acoustic output from ultrasound medical devices has been largely dictated by the Food and Drug Administration (FDA), empowered by an act of Congress. Until recently, the FDA regulated the maximum output of ultrasound devices to a predicate level through a marketing approval process which requires that devices be equivalent in efficacy and output to those produced prior to 1976. Diagnostic ultrasound technology now allows discrimination of fine detail and improved diagnostic sensitivity has been accompanied by substantial increases in acoustic output. The FDA now provides an option for manufacturers to obtain market approval for medical ultrasound devices that can substantially increase the acoustic output over previously allowable levels, provided that an output display is incorporated into the equipment design. Based on these changes in acoustic output regulation and recent evidence of potential biological effects of ultrasound at clinical output levels, the American Institute of Ultrasound in Medicine (AIUM) is sponsoring a conference to assess the scientific evidence associated with the mechanical effects of ultrasound, such as cavitation. In the months leading up to this conference a document will be developed to provide the ultrasound community with an overview of the scientific information, summary statements, and any recommendations concerning the safety of diagnostic ultrasound with respect to mechanical effects. AIUM has a record of providing this service to the ultrasound community to insure the safe and effective use of ultrasound in medical practice. To insure wide dissemination of this important information, request is made to help undersrite the publication cost of the resulting document as a supplemental issue in the Journal of Ultrasound in Medicine.